1. Field of the Invention
The present invention is directed to a process for the production of hydroxy-diphosphonic acid derivatives of higher carboxylic acids.
It has more specifically as an aim the production of said derivatives of carboxylic acids slightly soluble in water, that is carboxylic acids having more than 13 carbon atoms.
This new process is more specially adapted to produce hydroxy-diphosphonic derivatives of carboxylic acids having more than 15 carbon atoms.
2. Description of the Prior Art
The technique for producing hydroxy-diphosphonic acid derivatives of lower carboxylic acids has been known for many years, especially for the derivatives of acetic acid.
Nevertheless, the yields of such known processes are relatively low and these yields drop even more when one attempts to hydroxy-diphosphonate carboxylic acids having more than 13 carbons.
The HENKEL company, in its Belgian Pat. No. 619,600, describes a process which produces diphosphonated acids containing large quantities of the starting compounds, at relatively low yields in relation to the phosphonating reagent added (on the order of 30% of phosphorus converted into hydroxy-diphosphonic acid). This has been verified by using this technique for the conversion of fatty acids having a relatively high number of carbons. In this regard, one may refer to the comparative experiment below which reproduces for stearic acid the conditions described in this Belgian patent (corresponding to the U.S. Pat. No. 4,060,546).
More recently, the ALLIED CORPORATION has obtained U.S. Pat. No. 4,316,877 where the technique of the preceding patent is utilized for the manufacture of extracting compositions. Nevertheless, as will be seen in the comparative example which follows, this process does not improve markedly that described in the HENKEL patents.
The compounds produced by diphosphonating carboxylic acids are of growing interest, especially those compounds having a sufficiently high number of carbons to be liposoluble while being very hydrophobic, for the extraction by ion exchange of different metals, especially uranium, from highly acidic mediums or very chelating mediums, such as is described in European Patent Application No. 81,400633,4.
In general, it is not acceptable to have low yields vis-a-vis the reagents used for any organic product whose cost governs the use in industrial processes.
In addition, in the patents mentioned above, one by-product of the reaction, phosphorous acid, is not reusable since non-used during the reaction. This is the reason why research which has been carried out leading to the present invention has concentrated on the use of this by-product in as high a quantity as possible.